This invention relates broadly to the art of continuous and semicontinuous metal casting systems, and more particularly, to such systems wherein electromagnetic inductors serve to shape molten metal prior to solidification thereof.
Prior-art patents disclosing electromagnetic casting systems of the type to which this invention relates include U.S. Pat. Nos. 3,467,166 to Getselev et al., 3,605,865, 3,702,155 and 3,773,101 to Getselev, 3,735,799 to Karlson, and 3,985,179 and 4,004,631 to Goodrich et al.
These prior-art patents describe a system for continuously and semicontinuously electromagnetically casting wherein molten metal is first introduced at a controlled rate into a bottom block, or pan, located within a loop-shaped inductor to form an embryo ingot. The bottom block is then lowered at a controlled rate with metal flow being controlled in accordance with this rate to form an ingot. The molten metal so introduced is confined laterally by electromagnetic forces generated by an alternating current in the inductor. The molten metal is thus formed into a shape in a horizontal plane similar to, but smaller than, the inductor. The emerging ingot is solidified in this shape by the application of a coolant such as water.
In most of these systems there is a tapered electromagnetic shield, or screen, located inside the inductor arranged coaxially therewith made of a non-magnetic, but electrically conductive, metal. The shield serves to attentuate the magnetic field of the inductor upwardly, thereby lessening the electromagnetic forces restraining the ingot at the top as opposed to those at the lower edge of the shield. The advantages of such a shield are fully described in U.S. Pat. No. 3,605,865 to Getselev, and the information in that patent is incorporated by reference herein. In practice, it has been found that these loop-shaped shields have warped very quickly. This warping is due to the large amount of energy that the shields have to absorb. Such distortion of the shields not only changes the magnetic fields, and thereby changes the shapes of the outer surfaces of shaped ingots, but also sometimes changes the point of coolant impingement on ingots, because coolant drops onto the ingots from the lower tips of the shields.
Thus, it is an object of this invention to provide a shield for electromagnetic continuous casting which does not warp as easily as prior art shields.
Another difficulty with prior-art shields is that they normally must be cooled to dissipate the large amounts of energy they absorb from the heat of the molten metal and from the electromagnetic fields. This cooling of the shields causes problems in that water falling from the lower tips of the shields contacts the ingots in a nonuniform manner, even when the shields are not warped as is described above. It is possible to design systems in which water falls from the lower tips of the shields without hitting the ingots, but even in these cases, this water interferes with water from separate spray units which spray onto the ingots.
Thus, it is another object of this invention to provide a shield for an elecromagnetic continuous casting system which must not be cooled.
It is a further object of this invention to provide a shield for an electromagnetic casting system which provides protection for personnel and equipment (including the inductor) surrounding an electromagnetic casting station.
It is another object of this invention to provide a shield for an electromagnetic casting system which can be easily repaired upon the warping thereof or upon contacting molten metal in an ingot.